Hydrogels can be generally characterized as having a cross-linked polymer matrix (elastomer) component that swells when contacted with a sufficiently compatible fluid (generally, water and/or water-compatible compounds). Polymeric microparticles that have become swollen due to fluid trapped within the matrix are referred to as hydrogel microparticles. Since active ingredients and other compounds can be contained within the matrix, hydrogels and hydrogel microparticles (as well as pastes and powders made therefrom) have been found to be useful for the encapsulation and delivery of such compounds in a variety of applications. For example, hydrogels and hydrogel microparticles are particularly useful for encapsulation and delivery of pharmaceutical agents, vitamins, fragrances, oils, and other compounds in personal care and healthcare applications. In particular, hydrogels and hydrogel microparticles are useful for absorption and delivery of water-soluble and alcohol-soluble actives. However, such gels and microparticles may have limited resistance to pre-mature release of the actives contained therein when exposed to aqueous and/or alcohol systems.
Although various methods of preparing hydrogels, and hydrogel microparticles are known, there remains a need for methods of readily modifying hydrogels and hydrogel microparticles for use in a variety of applications. For example, there remains a need for methods of adapting a water-dispersible hydrogel or hydrogel microparticle to modulate the ingress or release of water from or to its environment.